Proton coupling and anion effects in molybdenum model compounds

180 Abstracts B125

PROTON COUPLING AND ANION EFFECTS IN MOLYBDENUM MODEL COMPOUNDS R.C.Bray(a), R.Durant(b), G.J.Leigh(a). [(a) University of Sussex, Brighton, U.K. (b) University of Paisley, PA1 2BE, U.K.]

The model compound Mo02mpeH2 has been reduced by a novel route generating the species [MoOmpeH2]+.

Reaction of the

reduced species with the strong acids CF3S03H and CF3S03D allows EPR detection of a weak proton coupling to Molybdenum(i).

Though strong proton couplings for model

compounds have been previously reported, this is the first report of a weak coupling and is of interest because of similar couplings occurring during turnover in MO-enzymes. Investigation of couplings arising from Cl-, Br' and Iindicate strong interactions of these anions along the Mo=O axis and comparison of g values clearly shows that a previous report(ii) of [MoOmpeH2]+ was in error -. the true nature of the species seen was [MoOmpeH2Cl].

(i)

Measured Line Widths (in gauss-measured at half maxm.) 81

82

83

[JQI-[Ql

19.2 18.6 0.6

21.6 19.8 1.8

28.8 26.4 2.4

[MoOmpeH2]+/Cl' [MoOmepD2]+/Cl'

20.7 20.7

24.0 22.0 2.0

26.4 24.4 2.0

[MoOmpeH2]+ [MoOmpeD2]+

[JQl-[D21

0.0

(ii) J.T.Spence, M.Minelli, P.Kroneck.

(*) mpeH4 = [HS-C(CH3)2CH2&H2]2.

J.Amer.Chem.Soc.